Process and installation for producing molten steel of scrap

Abstract

There is disclosed a process for the production of molten steel or steel pre-products from scrap contaminated with combustible waste-like substances and heated and melted in a metallurgical meltdown vessel. In order to be able to dispose of the forming noxious substances at low costs and to keep the offgases free of impurities detrimental to the environment, the gas forming during charging of scrap into the metallurgical vessel and during heating and melting of the scrap, after conditioning to a temperature range of between 1000° and 1500° C., is used as a heating gas in a lime-burning process including a moving lime fixed-bed under release of its sensible heat. Sulfur- and chlorine-containing components of the heating gas are absorbed on the burnt lime and the dust contained in the heating gas is separated in the lime fixed-bed. The heating gas, which is purified and cooled at its passage through the lime fixed-bed, subsequently is finally purified in a filtering plant.

What we claim is: 
     
       1. A process for the production of molten steel or steel pre-products from scrap contaminated with combustile gas-forming waste substances which comprises: providing a metallurgical meltdown vessel,   preheating and charging said contaminated scrap into said meltdown vessel during the preheating of which a first offgas is formed,   further heating and melting said charged scrap during which a second offgas is formed,   combining said first and second offgases,   conditioning said combined first and second offgases to a temperature in the range of about 1000° C. to 1500° C.,   directing said combined and heated first and second offgases as a heating gas to and through a lime kiln to convert lime therein to burnt lime, wherein any sulfur and chlorine contained in said heating gas are absorbed by said burnt lime and dust contained in said heating gas is separate during passage of said heating gas through said kiln, following which a pre-purified and cooled gas is obtained, and   then further purifying said pre-purified and cooled heating gas by passing it through a filtering plant.   
     
     
       2. A process as set forth in claim 1, further comprising pre-heating said scrap outside of said metallurgical meltdown vessel under formation of offgas, mixing said offgas with said gas forming during melting, and using said offgas commonly with said gas forming during melting as a heating gas in said lime burning process. 
     
     
       3. A process as set forth in claim 1, further comprising homogenizing and completely reacting said heating gas after conditioning to a temperature range of between 1000° and 1500° C. in a mixing chamber. 
     
     
       4. A process as set forth in claim 1, wherein dust incurred in said filtering plant, commonly with dust incurred in said lime burning process and including fine lime, is recycled into said meltdown vessel as a slag-former. 
     
     
       5. A process as set forth in claim 4, wherein said dust is blown into said meltdown vessel. 
     
     
       6. A process as set forth in claim 4, further comprising briquetting said dust so as to obtain briquets and charging said briquets into said meltdown vessel. 
     
     
       7. A process as set forth in claim 6, wherein said briquets are charged into said meltdown vessel commonly with lump line. 
     
     
       8. A process as set forth in claim 1, wherein an induction draught ventilator is provided to follow said final filtering for sucking off said heating gas from said meltdown vessel and moving it through said lime fixed-bed. 
     
     
       9. In an installation for producing molten steel or steel pre-products from scrap contaminated with combustible gas-forming substances, said installation including a metallurgical meltdown vessel provided with an offgas duct for conducting offgases formed during charging and melting of scrap in said vessel, said vessel being surrounded by an enclosure having an exhaust duct connected thereto, the improvement; wherein said offgas duct of said metallurgical meltdown vessel extends into said exhaust duct of said enclosure and further comprising:   burners provided in said exhaust duct,   a mixing chamber connected forwardly of said exhaust duct for receiving said offgases,   a lime shaft kiln connected to said exhaust duct forwardly of said mixing chamber and containing a moving lime fixed bed,   a further exhaust duct extending from said lime kiln to a filtering plant,   an induced draft ventilator connected forwardly of said filtering plant to draw said treated offgases through said filtering plant, and   a stack connected forwardly of said draft ventilator for disposing of treated gas therethrough.   
     
     
       10. An installation as set forth in claim 9, further comprising an oxygen-containing gas feeding duct entering said exhaust duct. 
     
     
       11. An installation as set forth in claim 9, wherein said mixing chamber provided in said exhaust duct is comprised of a thermoreactor. 
     
     
       12. An installation as set forth in claim 9, wherein said mixing chamber provided in said exhaust duct is comprised of a hot-gas cyclone. 
     
     
       13. An installation as set forth in claim 9, further comprising a dust bin and dust evacuation duct means leading from said lime shaft kiln and from said filtering plant to said dust bin. 
     
     
       14. An installation as set forth in claim 13, further comprising a dust recycling duct leading from said dust bin to said meltdown vessel. 
     
     
       15. An installation as set forth in claim 13, further comprising a briquetting plant arranged after said dust bin and a briquet-conveying means leading from said briquetting plant to said meltdown vessel.